A horse which arose from the water during the samudra manthan. As soon as he saw it, Indra took ownership and from then on, it became his vehicle as per Mahabharata Adiparva Chapter 28 verse 33-37.

As per Mahabharata Adiparva Chapter 27, Kashyapa’s wives Vinata and Kadru gave birth to Garuda and the nagas respectively. Once Vinata said that the tail hairs of Indra’s horse Uchaishravas were all white, Kadru maintained that it was black. It was agreed that whoever lost would become the other’s slave. As per Kadru’s instructions, a few nagas clung to the horse’s tail and made it appear black. Thus Vinata became Kadru’s slave and Garuda had to take care of Kadru’s children.

Once Revanta, Surya’s son and Indra’s friend, rode Uchaishravas to Vaikuntha to see Vishnu. Lakshmi, who was by Vishnu’s side was amazed at seeing her brother Uchaishravas and sat staring at him. She didn’t hear Vishnu speaking to her. Vishnu cursed her and as a result she was born as a mare. From that form was created the Hehaya clan as per Devibhagavata Skanda 6. See Ekavira.